You have to change the "compatibility settings" for JabRef to "Disable scaling for high DPI settings". Further information is available at https://support.microsoft.com/en-us/topic/windows-scaling-issues-for-high-dpi-devices-508483cd-7c59-0d08-12b0-960b99aa347d
Further reading: https://github.com/JabRef/jabref/issues/415 and http://discourse.jabref.org/t/jabref-3-6-on-hires-laptop-screen-messed-up/277.
You can directly use the references in Word's internal reference manager. Short explanation: Export your bibliography in XML format and replace the Sources.xml in %APPDATA%\Roaming\Microsoft\Bibliography. Long explanation: check out Export to Microsoft Word. Also, see https://www.youtube.com/watch?v=2PpLZTol9_o for a video explaining how to add and how to cite references in a Word document.
Another option is to use Bibtex4Word. See https://www.youtube.com/watch?v=9j3g4wfdM00 for a video explaining the usage.
The last option is to use Docear4Word, which is planned to be ported to JabRef (see JabRef4Word).
Use AutoHotkey and JabRef.ahk provided at koppor's autohotkey scripts.
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A: On Windows, one finds the log files in %APPDATA%\..\Local\org.jabref\jabref\Logs\{version}. {version} indicates the currently used JabRef version.
A: According to source, you may have to set the font manually by downloading the Base.css from Custom themes - JabRef. Then open the Base.css, and add the following text at the end of Base.css: